Since hairy cell leukemia was first described in 1958 (Bouroncle, B. A., Wiseman, B. K., Doan, C. A. Blood 13, 609 (1958)) the nature and cellular origin of this malignancy have been controversial. Originally termed "leukemic reticuloendotheliosis" due to the major involvement of the RES, it has become known under the more popular designation "hairy cell leukemia" by Schreck and Donnelly in 1966 (Schreck, R., Donnelly, W. J., Blood 27: 199, (1966)).
The diagnosis hairy cell leukemia is presently based on the electron and light microscopy appearance (Wright stain, supravital stain, phase contrast, slide chamber) of the leukemic cell. Typical ribosome-lamellar complexes in ultrastructural investigation have been observed prevalently in hairy cells but are also known in other malignancies (Daniel, M. T., Flandrin, G., Lab. Invest. 30: 1, (1974); Katayama, I., Li, C. Y., Yam, L. T. Am. J. Pathol. 69: 471, 1972; Katayama, I. Schneider, G. B. Am. JU. Pathol. 86: 163, (1977)). Furthermore, the diagnosis is supported by the evidence of tartrate resistent acid phosphatase (TRAP) first discovered by Yam et al. (Yam, L. T., Li, C. Y., Lam, K. W. N. Engl. J. Med. 284: 357, (1971). However, the latter phenomenon is indicative but not specific for hairy cell leukemia, and some hairy cells do not express this cytochemical marker (Katayami, I. Yang, J. P. S. Am. J. Pathol. 68: 268, (1977)). The resemblance to B-lymphocytes is obvious. Surface immunoglobulin is present with one or more heavy chain and monoclonal light chain expression. Presence of HLA DR antigen (Jansen, J., Turcker, W. L. B., Kersey, J. H. Blood 59: 609, (1982)), and absence of C3 receptor (Burns, G. F., Cawley, J. C., Barker, C. R., Hayhoe, F. G. J. Clin. Exp. Immunol. 29: 442, (1977)) are also characteristic findings in the majority of hairy cells.
Phagocytosis of latex particules and bacteria has been frequenctly described in in vitro studies of hairy cells (Polliack A. Braylan, R., Golomb, H. Lancet 2: 1013, (1974); Daniel, M. T., Supra (1974)). However, based on more recent reports, it is controversial whether a real internalization of those particles takes place or whether they get trapped within the extracellular space between the pseudopods (Jansen, J., Meijer, C. J. L. M., van der Valk, P., de Bruyn, W. C., Leijh, P. C. J., den Ottolander, G. J., van Further, R. Scand. J. Haematol. 23: 69, (1979)).
Accordingly, more specific, sensitive and reliable diagnostic tests for hairy ell leukemia have been sought.